package org.bouncycastle.crypto;

import java.math.BigInteger;

/**
 * interface for classes implementing the Digital Signature Algorithm
 */
public interface DSA {
    /**
     * initialise the signer for signature generation or signature verification.
     * 
     * @param forSigning
     *            true if we are generating a signature, false otherwise.
     * @param param
     *            key parameters for signature generation.
     */
    public void init(boolean forSigning, CipherParameters param);

    /**
     * sign the passed in message (usually the output of a hash function).
     * 
     * @param message
     *            the message to be signed.
     * @return two big integers representing the r and s values respectively.
     */
    public BigInteger[] generateSignature(byte[] message);

    /**
     * verify the message message against the signature values r and s.
     * 
     * @param message
     *            the message that was supposed to have been signed.
     * @param r
     *            the r signature value.
     * @param s
     *            the s signature value.
     */
    public boolean verifySignature(byte[] message, BigInteger r, BigInteger s);
}
